In the prior art, the use of heat exchangers to cool engine fluids is well known. Various types of exchangers have been proposed, including types to ease installation, reduce drag and improve heat transfer efficiency.
U.S. Pat. No. 4,557,319 to Arnold discloses a marine keel cooler having fore and aft headers that are spaced apart in a parallel relationship and connected by a plurality of tubes or pipes extending normal thereto. The headers are streamlined and fixed to the bottom of a marine vessel with the tubes spaced outwardly from the vessel's bottom and extending longitudinally therewith. In Arnold, the tubes are disposed between the headers.
U.S. Pat. No. 3,841,396 to Knaebel et al. discloses a heat exchanger that performs two basic purposes. First, the heat exchanger provides a passageway through a longitudinal member which integrally incorporates a series of radial disposed fins for enhanced heat exchange. Second, the heat exchanger incorporates flange means integral with the longitudinal member to provide for flush and stable mounting of the device to a supporting surface. The heat exchanger of Knaebel reduces drag on its hull during movement. The cooling tubes of this heat exchanger are disposed between the opposing headers.
U.S. Pat. No. 3,240,179 to Van Ranst discloses a cooler adapted to be used with marine vessels to provide cooling for propulsion engines. This cooler provides relatively large effective heat exchange areas in proportion to the size of the complete unit and has flow characteristics on both internal and external surfaces to provide a highly efficient heat exchange unit. The cooler of Van Ranst has a bottom or outer sheet portion which has a transverse sinuous configuration. The cooler is designed so that the upper or inner ends of the tube convolutions formed by the sinuous outer sheet portion are disposed substantially in the plane of the skin bottom. Thus, the headers of the cooler are disposed within recesses in the vessel hull.
The prior art discussed above, while providing more efficient heat exchange and less drag, is still not without its disadvantages. The cooler of Van Ranst is complex in nature so as to require extensive manufacturing time and is adapted to fit only certain types of vessel hulls, those having recesses. The heat exchangers such as those disclosed in Arnold and Knaebel et al., while being streamlined in shape, compromise heat transfer efficiency with improvements in drag.
Consequently, a need has developed to provide more efficient heat exchangers for marine use. The present invention solves this need by providing a marine heat exchanger that has an improved header configuration which combines both reduced drag and improved heat transfer.